Motor drives and other forms of power conversion systems convert electrical power from one form to another and may be employed in a variety of applications such as powering an electric motor using power converted from a single or multiphase AC input source, converting AC power from a wind driven generator to supply power to a grid, etc. Power converters may include multiple stages for different types of conversion applications, such as AC/DC/AC drives for electric motors having a pulse width modulated (PWM) active current source rectifier in which AC input power is selectively switched to create a DC output bus voltage from which a load is driven by a PWM controlled inverter stage. This type of converter is particularly useful in driving electric motors in industrial applications requiring variable speed control with varying motor load situations. Control of harmonics in such power conversion systems is a continuous challenge, particularly where an active input converter stage is used to interface with the utility grid. Conventional approaches to harmonic spectrum control include the use of predetermined rectifier firing angles for selective harmonic elimination (SHE), as well as the provision of hardware-based input filter circuits at the rectifier input. However, these techniques have thus far provided only limited success in controlling total harmonic distortion (THD) and input filter circuits are expensive. A continuing need therefore exists for improved motor drives and harmonic control techniques in motor drives and other switching-type power conversion systems.